The present invention relates to a shift device, and more particularly to a shift device for coupling a gear to a shaft a shift sleeve carrier is operatively fixedly arranged relative to the shaft, an outer axial coupling toothing is immovably arranged relative to the gear and concentric to a rotation axis of the shaft, an outer axial driving toothing immovably arranged relative to the shift sleeve carrier and concentric to the rotation axis and in alignment with the outer coupling toothing, an annular shift sleeve arranged concentrically to the rotation axis and for axial movement relative to the shaft, an inner axial coupling toothing immovably arranged relative to the shift sleeve and concentric to the rotation axis and in alignment with the outer coupling toothing, a synchronizer ring arranged concentric to the rotation axis and axially between the gear and the shift sleeve carrier for axial and rotational movement relative to the gear and the shaft, an outer locking toothing immovably arranged relative to the synchronizer ring and concentric to the rotation axis and in alignment with the outer coupling toothing, stops for limiting rotation between the synchronizer ring and the shaft, a pair of friction surfaces which has one friction surface associated with the synchronizer ring and one friction surface associated with the gear and is operable to be brought into frictional connection by axial relative movement of the synchronizer ring in a direction of the gear axially immovably arranged relative to the shaft, an annular shaped coil spring element closed upon itself in a peripheral direction thereof and arranged both concentrically to the rotation axis and axially between the driving toothing and the locking toothing, said element being mounted at each of a number of points on a periphery thereof on a respective supporting element immovable relative to the synchronizer ring, and at least one tooth of the inner coupling toothing arranged in a peripheral region between two supporting elements and has a radial overlap with the shaped coil spring element and, on an end face thereof facing the gear, has an inclined surface inclined relative to the rotation axis for engagement on the shaped coil spring element, whereby a root circle of the inner coupling toothing and an addendum circle of the driving toothing each lies concentrically to the rotation axis, the inner coupling toothing engages in matching driving toothing for rotational movement therewith and axial movement therealong, teeth of the inner coupling toothing which lie in a supporting element peripheral region are radially non-overlappingly arranged with respect to the shaped coil spring element, the inclined surface has a larger diameter at an end thereof facing the gear than at another end opposite the gear, the shaped coil spring element is supported substantially rigidly, relative to the synchronizer ring, in a direction of the rotation axis towards the gear, and, in respect of portions thereof lying between the supporting elements in the peripheral direction, resiliently in a centripetal direction, and that the number of points is an integral multiple of 1.
U.S. Pat. No. 3,700,083 shows the shift device in which the addendum circle of the inner coupling toothing of the shift sleeve and the root circle of the driving toothing of the shift sleeve carrier are also formed concentrically to the axis of rotation of the shaft. Consequently, the teeth of the inner coupling toothing which lie in the region of the supporting elements and which constitute the majority of the teeth of the inner coupling toothing must be markedly shortened. This shortening must be provided in order to avoid radial overlapping with the shaped coil spring element which cannot deflect radially inwards at that point so that when synchronism exists the inner coupling toothing of the shift sleeve can penetrate unhindered into the outer coupling toothing of the gear over the locking toothing of the synchronizer ring. The useful area of the inner coupling toothing is thereby greatly reduced and thus the surface pressure is increased. This is the case both during the synchronization and during torque transmission with the gear speed engaged.
An object of the present invention is to keep the reduction of the useful area of the inner coupling toothing as low as possible.
The foregoing object has been achieved according to the present invention by providing that an addendum circle of the inner coupling toothing and the root circle of the driving toothing are each composed of a number of circular lines which lie eccentrically relative to the rotation axis, the centers of the circular lines lying in separate planes which each case the rotation axis and are directed centrally relative to a supporting element, the number of circular lines being at least 2.
Because of the shift sleeve profile formed by eccentric circular lines, the shift device according to the present invention avoids the disadvantage of an excessively reduced area of the toothing inasmuch as each tooth is shortened only to the necessary extent.